Dozens of Yemenis loyal to President Abd Rabbuh Mansour Hadi's government have been arrested since his forces pulled out from Aden, southern secessionists said on Saturday.

Following the latest offensive in a see-sawing month-long conflict in Yemen's south, pro-government forces on Thursday retreated from areas of Aden city that they had captured the day before.

The Security Belt Forces (SBF), the military wing of the Southern Transitional Council (STC), pushed Hadi's troops back to areas of nearby Abyan province with the help of Emirati air strikes and reinforcements redeployed from the north.

The United Arab Emirates' air strikes killed more than 40 of Hadi's troops, which are backed by UAE ally Saudi Arabia. The two are ostensibly partners in the Saudi-led coalition fighting the Houthi rebel movement in the north.

Once the pro-government forces left Aden on Thursday, the SBF raided homes and businesses across the city, detaining "scores" of pro-Hadi activists, politicians and clerics, accusing them of "terrorism," STC officials and witnesses told Reuters news agency.

Arrests continued on Saturday, as southern fighters patrolled Aden's streets.

Residents told Reuters that an uneasy calm surrounded the city.

Sources told Middle East Eye that Hadi's forces, under the command of Brigadier Abdullah al-Sobaihi, were massing around the Abyan province village of al-Alam, a traditional gateway to Aden.

The conflict in south Yemen is essentially a civil war within a civil war.

Yemen has been at war since 2014, when the Houthi movement chased Hadi's government out of the capital Sanaa, prompting the Saudi-led coalition to intervene on its behalf.

The UAE is a key player in the coalition, but has begun a troop redeployment in an attempt to hand more control and responsibility on the front lines to its Yemeni proxies, such as the STC.

However, earlier this month the southern secessionists turned on their erstwhile ally Hadi, chasing his forces out of Aden, Abyan and much of the surrounding area.

South Yemen: Timeline of a civil war within a civil war

1 August: A missile attack claimed by the Houthis kills dozens of Security Belt Forces (SBF) officers at a military parade near Aden, including a leading SBF commander, Brigadier General Munir “Abu al-Yamama” al-Yafee. The Houthis claim responsibility, but the UAE-backed Southern Transitional Council (STC), the SBF's political wing, blame the attack on al-Islah, which it said had infiltrated President Abd Rabbuh Mansour Hadi's government and military, including the presidential guard stationed at al-Maashiq presidential palace in Aden.

7 August: Gunshots are reportedly fired at Yafee's funeral, which was held near Aden's presidential palace. Fighting breaks out between SBF fighters and presidential guards at the palace entrance. The STC claims 11 of its members were killed in the exchange of fire. Later that evening, STC Vice Chairman Hani bin Breik calls for supporters to march on the presidential palace to overthrow Hadi's government.

8 August: At least 12 people are killed in renewed clashes between the SBF and pro-Hadi forces in Aden.

10 August: The STC captures Aden after a fierce battle with loyalist forces. At least eight civilians are killed in the fighting. The Saudi-backed government accuses the STC of staging a coup in the southern port city after its fighters seized all military camps, prompting Riyadh to call for an urgent meeting for the warring parties.

20 August: SBF fighters encircle a pro-government special forces camp in the Zinjibar, the capital of Abyan province. The special forces camp and a nearby military base both fall under the control of the SBF.

22 August: The Shabwani Elite Forces (SEF), a militia loyal to the STC, attacks government forces in the Shabwa province and captures several areas, including its capital city of Ataq.

28 August: Pro-government forces recapture Abyan province and Hadi's information minister announces Aden has been taken back and its presidential palace seized.

29 August: STC forces regain parts of Aden city and Abyan province. The UAE claims responsibility for airstrikes against what it calls "terrorist organisations", and Hadi calls on Saudi Arabia rein in the separatists, saying his forces have withdrawn from the city to prevent further destruction.

After early gains, the SBF and its allies came across fierce, Saudi-backed resistance in Shabwa province, and pro-government units forced their way back towards Aden, briefly claiming control of the city on Wednesday.

The SBF contains thousands of fighters armed and trained by the UAE, and wishes to restore the republic of South Yemen that was independent between 1967 and 1990.

The insecurity in Yemen’s south has also provided a platform for militant attacks, with an Islamic State group-claimed bomb attack on Friday killing six separatist fighters on Aden's outskirts.

Hadi, who is based in Riyadh, has called on Saudi Arabia to intervene and convince the UAE and its proxies in Yemen to end their attacks.